When did hams start paying attention to gray-line propagation effects?

Over the last few years I've learned quite a lot about what to expect for gray-line propagation, and the twilight effects on both the D and the F layers. I've had especially good results on the lower bands (80/40) with less-than-ideal antennas, working some great CW DX on 80 at the crack of dawn that would not have been possible 2 hours before or 2 hours after. I never paid attention to this phenomenon prior to 2010 or so.

But what I have noticed is there isn't much mention of gray-line prior to the Internet Age. In fact, almost none. I've checked all the ARRL handbooks I have going back decades, and there's no mention of gray-line at all in the sections on "propagation phenomena". At least none I've found.

It would appear that prior to the Internet, the only way to really visualize the terminator and resulting gray-line was to go out and spend a heap of cash on a Geochron mechanical sun clock, customized for your location. Now granted, the first Geochrons were sold in the early 1960s.

But realistically, only a tiny percentage of hams could afford one back then. You could certainly graph it on paper, but no sooner had you started graphing it would have changed again! Without a Geochron (in essence an analog computer) or modern digital computer, there really was no practical way to do this.

Lots of internet searching only turns up the myriad visualization programs and sites to view the gray-line at any moment in time, but nothing really describing the history of "hams paying attention to it" or other radio services for that matter (surely SW BC stations were aware of the phenomena and built schedules around the gray-line over the course of a broadcast year).

Curious: when did you start paying any attention to gray-line propagation effects? Does anyone know when the phenomenon was first noted in ham radio circles?

Dave
W7UUU

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Dave,

I heard about gray-line a couple of months ago in a different thread and noticed that every morning as the gray-line crossed the east coast of the US, Australia lit up for me. Day after day and week after week I noticed it and started leaving PSK Reporter up full screen on a separate monitor.

40 meter seems to be the best for me but it was something I learned about thru experience before I learned about it via research.

The DX Edge® was a plastic slide-rule day/night/gray-line tool developed by Tony Japha, N2UN(sk), who registered the name as a trademark and sold the device through a company called Xantek, Inc.

It consisted of a rectangular map of the world, with shaded clear-plastic overlays showing the day/night/gray-line pattern for each month of the year. By positioning the overlay on the map based on the time-of-day at the desired location, you could see which parts of the world were in daylight and which were in darkness and where the gray-line fell at that particular time. Sliding the overlay across the time scale demonstrated the movement of day/night and the gray-line.

I have often thought what would be cool is a project that mounted a spare, underutilized flat screen TV to the shack wall and connected it to a cheap Raspberry Pi computer, running software to emulate a Geochron mechanical clock. You wouldn't even have to set the set the time nor the date, as the Raspberry Pi would be connected over WiFi/Internet to a network time service.

I see they are now offering a more reasonably priced alternative, too, a widget that plugs into your TV with firmware that does their clock onscreen. For most of us a nice computer program is probably more practical if you don't want to pay for a real Geochron.

Would I love to have a mechanical Geochron? Heck yeah...but...the 2K + one requires would get me a good part of the way to a new IC-7610, and that's always been the problem.

Not quite the answer Dave UUU was after, this pre war radio times calculator, the centre wheel rotates and gives the times pm and am when the transmitting country can be recieved in your home country.

The centre wheel will give an indication of a grey line although I think in those days the grey was not known as such. Remember seeing the grey line globes shown by W6RZ as youngster in the 1950's/60's.

Not quite the answer Dave UUU was after, this pre war radio times calculator, the centre wheel rotates and gives the times pm and am when the transmitting country can be recieved in your home country.

The centre wheel will give an indication of a grey line although I think in those days the grey was not known as such. Remember seeing the grey line globes shown by W6RZ as youngster in the 1950's/60's.